Does your game company give things away for free? I bet it does.
Who are the people who download your demo, and play it over and over again?
Who are the people who play your website's free web games?
Who are the people that scour the convention floor for freebees?
And they haven't bought ANYTHING!
They are Tourists, and one of the best ways to get their attention is with free stuff. What you do with that attention, is up to you.
Some Tourists will never buy anything, no matter what you do. That's okay. Treat them right, but don't let them get in the way of potentials. The people who are interested in what you're selling. With them, you have their attention, you have something they're interested in. Now what?
That, of course, depends. We're selling trading cards. I think the biggest hurdle with a trading card product is making that first sale. That's a major threshold moment in your relationship with that person. That first sale elevates the person from Tourist to Customer. Everything Changes.
All your customers start out as tourists. The attention you get depends on how interesting you are to look at. What you can do with their attention determines how many become customers.